A. SELECT 学号,SUM(学分) AS 总学分 FROM SKB; WHERE 成绩>=60 AND 总学分>=8 B. SELECT 学号,SUM(学分) AS 总学分 FROM SKB; HAVING 成绩>=60 AND 总学分>=8 C. SELECT SKB.学号,SUM(KC.学分)AS 总学分 FROM SKB,KC; WHERE KC.课程号=SKB.课程号 AND SKB.成绩>=60; GROUP BY SKB.学号; HAVING 总学分>=8 D. SELECT SKB.学号,SUM(KC.学分)AS 总学分 FROM SKB,KC; GROUP BY SKB.学号; HAVING SKB.成绩>=60 AND 总学分>=8